Adjustable backrest for a tub



FIG. 1 is a front perspective view showing my new design for an adjustable backrest for a tub;

FIG. 2 is a rear elevational view;

FIG. 3 is a left side elevational view which is a mirror image of the right side elevational view;

FIG. 4 is a front elevational view;

FIG. 5 is a top plan view; and,

FIG. 6 is a bottom plan view.

The broken line drawings of the tub, amputee person and rib gussets are for environmental purposes only and form no part of the claimed design. 

CLAIM The ornamental design for an adjustable backrest for a tub, as shown and described. 